A U.K. study reveals mothers who take acetaminophen while pregnant are more likely to give birth to children with high levels of hyperactivity.
The study, published in medical journal JAMA Pediatrics, tracked mothers' use of acetaminophen while 18 and 32 weeks pregnant, as well as when their children were 61 months old, CNN reports.
Results revealed those mothers taking acetaminophen at 18 weeks pregnant were more likely to give birth to hyperactive children with behavioral issues.
By the 32nd week of pregnancy, there was a high chance the baby would also have emotional problems.
"This is actually the fourth major study to find acetaminophen use during pregnancy associated with neuro-development of the child," said Michele Marcus, a professor at Emory University Schools of Public Health & Medicine.
Statistics indicate half of all pregnant mothers use acetaminophen, the main ingredient in popular over-the-counter medications such as Tylenol. It is generally considered safe to take during pregnancy, reports CNN.
"Minor aches and pains (e.g. headaches or mild backache), are common in pregnancy and often are a reason for patients to take acetaminophen," said Dr. Aisling Murphy, assistant clinical professor at UCLA Obstetrics and Gynecology. "The practice is very common."
Some, including the U.S. Food and Drug Administration, criticize the design of research studies like these, which they say make them unreliable to draw conclusions from.
"It is important to note there are no studies demonstrating a causal link between acetaminophen use during pregnancy and adverse effects on child development," said Marc Boston, a spokesman for McNeil Consumer Healthcare, the maker of Tylenol.
Dr. Hal C. Lawrence, CEO of the American College of Obstetricians and Gynecologists, agrees with Boston's sentiments.
"Behavioral disorders are multifactorial and very difficult to associate with a singular cause," Lawrence said. "The brain does not stop developing until at least 15 months of age, which leaves room for children to be exposed to a number of factors that could potentially lead to behavioral issues."
"The takeaways here are that physicians should not change clinical practice until definitive prospective research is done and, most importantly, patients should not be frightened away from the many benefits of acetaminophen," he added.